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Poisonous snakes are a common characteristic. Characteristics of the snake detachment. The duality of the image in ancient mythology
Many people are afraid of snakes. At the same time, it is simply impossible not to note their features and uniqueness. Cold-blooded animals amaze with their behavior, an original way of movement, the strength of the effect of a poisonous substance and an unusual appearance. Snakes are among the chordates. Reptiles are included in the order scaly, suborder snakes. The existence and well-being of cold-blooded animals is greatly influenced by the ambient temperature. The study of snakes reveals the unpredictable traits of reptiles and is gaining a growing audience that cannot but fall in love with this population.
Characteristics and structure of snakes
Before recently 3200 species of snakes were known to science and only 410 species are poisonous. The most interesting and unusual feature of cold-blooded animals is the unique body structure. In length, an adult can grow up to nine meters. The smallest snakes grow up to 10 cm. The same fluctuations apply to the weight of representatives of the scaly order, starting from 10 g and reaching 100 kg. Home distinctive feature males is their long tail; they also grow smaller.
The variety of body shapes is simply amazing. There are individuals that have a long and thin body, or, conversely, a short and thick one. Those snakes that live near the sea have a flattened appearance and often resemble a ribbon. The skin of cold-blooded animals is mostly dry, completely covered with scales or peculiar shields. In different parts of the body, the surface is different, for example, on the sides and on the back, the scales are small and resemble tiles (since they overlap each other). The belly of most snakes is "dotted" with wide semicircular plates.
The eyelids of snakes are immobile and seem to be able to hypnotize the victim. Reptiles never blink and even sleep with open eyes. The unique structure of the skull allows even the smallest individuals to open their mouths enough for a small rabbit to fit into it. This is because the upper jaw is connected to adjacent bones and is mobile, while the elements of the lower jaw are connected by a ligament that is stretched.
Due to the unusual body, the structure of the organs is also unique: they are all elongated and elongated closer to the head. The skeleton has a total of about 200-400 vertebrae, each of which is mobile and connected by ligaments. The snake slides along the ground due to the movement of the shields located on the belly. Thanks to the keratinized layers of the epidermis, cold-blooded animals move quickly without difficulty.
Despite all the features of snakes, reptiles have poor eyesight and hearing. In return, nature endowed them with a wonderful sense of smell and touch. Not the last role in orientation in space is played by the tongue, which is forked at the end. Many researchers call it "sting". Opening its mouth, the snake catches air with its tongue and various particles and elements of the atmosphere stick to it, then the reptile brings the organ to a certain place located in the mouth and smells and tastes.
In most cases, snakes use their venom for self-defense, and this is also one of the ways to kill the victim.
Feeding and hibernation of snakes
What snakes eat depends on the size of the cold-blooded animal. The main diet of reptiles consists of rodents, some types of insects. But the fact remains that all snakes are carnivores. For individuals, it is considered a real delicacy to have breakfast with small chicks or eggs. Thanks to the ability to climb trees, they easily ruin bird nests and enjoy the meal.
Meals are not taken every day. Snakes cope well with hunger and, provided that there is water nearby, individuals may not eat for months. A feature of reptiles is their endurance and patience. Snakes hide among the foliage, wait for prey along the road or on the ground, but the hunt is patient and, as a rule, effective. Animal eaters swallow food from the head, but with caution, so as not to injure themselves from the sharp teeth of the victim. Before this process, individuals try to immobilize the animal by squeezing its body with their rings.
Digested food for 2-9 days. The speed of the process depends on the health of the individual, temperature environment, the magnitude of the victim. To speed up digestion, many snakes expose their abdomen to the sun.
Snakes do not like cold weather, therefore, already in late October - early November, they leave for the winter. Individuals can choose a rodent hole, a haystack, tree roots, cracks, crevices and other places as a dwelling. If reptiles are near people, then they hide in basements, sewer systems, abandoned wells. The hibernation of animals may be interrupted or not occur at all (if cold-blooded animals live in tropical or).
Toward the beginning of April, representatives of the squamous order begin to crawl out of their shelter. Exact time"out of torpor" depends on the level of humidity, temperature and other factors. Almost all spring, snakes bask in the sun. In summer, during the daytime, animals prefer to be in the shade.
Numerous families of snakes
Experts disagree on the number of families in the suborder of snakes. Here is the most popular classification of reptiles:
- Already-shaped - this family has more than 1500 species. Among them are a wide variety of snakes, differing in color, shape, pattern and habitat. Representatives of this group grow from 10 centimeters to 3.5 meters. They include aquatic and terrestrial, burrowing and arboreal cold-blooded. More than half of the snakes are non-venomous and are often kept in terrariums. However, false snakes are considered poisonous representatives of this group, as they have large teeth with grooves along which a dangerous substance flows.
- Vipers - the family includes more than 280 species. Most often, viper snakes are found on continents such as Asia, North America, Europe and Africa. The body length of cold-blooded animals varies from 25 cm to 3.5 m. Representatives of this family have light zigzag or rhombic patterns on their sides and back. All individuals have long fangs that secrete poison.
- Aspid - there are about 330 species of snakes. This group of reptiles is poisonous. Individuals grow in length from 40 cm to 5 m. You can meet cold-blooded ones on such continents as Asia, Africa, America and Australia.
- Blind snakes - the family includes about 200 species. Snakes of this group live almost all over the planet.
Thanks to the ability to adapt, snakes can be found in any part of the world. Despite belonging to the same family, animals have a variety of shapes, colors, differ in color, habitat and other features.
The brightest representatives of snakes
Among the wide variety of snakes, the most striking subspecies are snakes, vipers, asps, sea, pit-headed and false-footed cold-blooded. The following reptiles are considered the most interesting and unusual.
Hamadryand (royal cobra)
If you collect all the snakes together, then the Hamadryanda will surpass the rest. This type of animal-eating is considered the largest, even gigantic and poisonous. The king cobra grows up to 5.5 meters, there is no antidote after its bite today. Terrible poison in 15 minutes kills the victim. In addition, it is the Hamadriands that can eat their own kind. Females can starve for three months, carefully guarding their eggs. On average, cobras live for about 30 years and most often they can be found on the territory of the state of India and the islands of Indonesia.
Desert taipan (fierce snake)
It is quite possible to meet a land killer in the desert or on the plains of Australia. Quite often, individuals of this species grow up to 2.5 meters. The venom of a cruel snake is 180 times more powerful than that of a cobra. The color of a cold-blooded animal depends on weather conditions. So in the heat, taipans have straw-like skin, and in the cold - dark brown.
Black Mamba
The maximum height of the black mamba is 3 meters. The representative of reptiles is considered the fastest (individuals can move at a speed of 11 km / h). A venomous snake kills its prey in just a few seconds. However, the animal is not aggressive and can attack a person only when it feels threatened. The black mamba got its name because of the color of the mouth strip. The skin of a predator is olive, green, brown, sometimes with an admixture of metal.
Cassava (Gaboon viper)
Big, fat, poisonous - this is how the Gaboon viper can be characterized. Individuals grow up to 2 meters in length, and have a body girth of almost 0.5 meters. The main feature of the animals is the unique structure of the head - it has a triangular shape and small horns. This type of snake can be classified as calm. The females are viviparous.
Anaconda
Anacondas are included in the family of boas. These are the largest snakes, the length of which can be 11 meters and weight - 100 kg. "Water boa" lives in rivers, lakes, creeks and belongs to non-poisonous reptiles. The main food of cold-blooded animals is fish, waterfowl, iguanas and caimans.
Python
A giant non-venomous snake, reaching 7.5 meters in length. Females differ from males in their powerful body and large size. Pythons prefer to eat small to medium sized mammals. They can easily swallow a leopard, a jackal and digest prey for many days. Snakes of this type incubate eggs, maintaining the desired temperature.
Egg-eaters (African egg snakes)
Animals feed exclusively on eggs and grow no more than 1 meter in length. Due to the unique structure of the skull, small snakes easily swallow large prey. The cervical vertebrae break the shell, and the contents of the eggs are swallowed, the shell is expectorated.
radiant snake
Non-venomous snakes with excellent body color. Individuals grow up to 1 meter and feed on lizards, small rodents.
Worm Snake
Small representatives of reptiles (length does not exceed 38 cm) look like earthworms. They can meet under a stone, in thickets of bushes, rocky slopes.
Non-venomous snakes
Non-poisonous snakes include the following representatives of cold-blooded animals:
ordinary snake
Common snake - distinctive features are yellow or orange spots located on the sides of the head;
Amur snake
Amur snake - the length of the animal can reach 2.4 m, belongs to the already-shaped family;
Copperhead common
Also among non-venomous snakes include the tiger and reticulated python, milk snake, maize, yellow-bellied and Aesculapius snake.
tiger python
reticulated python
milk snake
yellow-bellied snake
Poisonous snakes
Gyurza
Gyurza is one of the most dangerous poisonous snakes. The length of individuals rarely exceeds two meters.
In Asia, there is such a dangerous predator as efa. Snakes of this type are afraid of people and warn them of their presence by hissing. Cold-blooded snakes grow up to 80 cm and are viviparous snakes.
A special place in the list of poisonous snakes is given to rattlesnakes (pit-headed) representatives of reptiles. They are one of the most dangerous animals on the planet and are known for their rattle-like tail.
snake breeding
Cold-blooded animals love to be alone. But during the mating season, they become very friendly and loving. The "dance" of males can last for many hours before the female consents to fertilization. Most snakes are egg-laying animals, but there are some species that give birth to live young. A snake clutch can reach 120,000 eggs (this process is influenced by the habitat and the type of reptile).
Sexual maturity in snakes occurs in the second year of life. The female is searched for by smell, after which the males wrap around the body of the chosen one. Surprisingly, the parents of newborns do not pay the slightest attention to them.
Conclusion
Snakes are extraordinary creatures that differ from each other in size, shape, skin color and habitat. Unique body structure interesting image life and character of individuals makes them a bright object for research.
Question 1. What acquired structural features allowed reptiles to completely switch to a terrestrial way of life?
Adaptations of reptiles to a terrestrial way of life:
1) keratinization of the skin and the absence of glands that would moisturize the skin, which is associated with saving water, protection from evaporation;
2) pulmonary respiration, which provides oxygen from the atmosphere;
3) ossification and development of the skeleton (especially the cervical and thoracic spine, free limbs and their belts) and muscular system, which allows you to actively move in a less dense than water, ground-air environment;
4) internal fertilization, the laying of fertilized eggs with a large supply of nutrients, covered with protective shells, which gives complete independence from the aquatic environment in reproduction.
Question 2. What are characteristics snakes?
Snakes do not have free limbs. They have developed a special mechanism of movement by lateral bending of the spine and ribs. Snakes have poor vision and poor hearing. They have no external auditory opening. The eyes are hidden under a transparent leathery film formed by fused eyelids (unblinking gaze). Poisonous snakes in the upper jaw have two particularly prominent poisonous teeth. Venom is produced by paired venom glands located on both sides of the head behind the eyes. Their ducts are connected with poisonous teeth.
All snakes are predators. They are able to swallow prey many times the thickness of their body. This is facilitated by special joints of the jaws. The lower jaw is movably connected to the bones of the skull and is able to move forward and go back, as if on a hinge. Its halves are connected on the chin by a flexible ligament and can be moved apart.
Question 3. What functions does the tongue of snakes forked at the end perform?
The tongue of snakes is the organ of touch, smell, and taste. Through a semicircular opening in the upper jaw, the tongue can protrude outward when the mouth is closed. By sticking out and removing the tongue, the snake receives information about the smells in the air, and when the tongue touches the surrounding objects, it receives information about their surface, shape and taste.
Question 4. What is the meaning of squamous in nature and human life?
Most scaly reptiles are carnivores or insectivores. Many species of snakes feed on rodents, regulating their numbers in nature.
Poisonous snakes can be dangerous to human life and health, but only in case of careless or inattentive behavior. The venom of some snakes (for example, the spectacled snake - cobra) is very valuable; various medicines are made from it.
Question 5. In this connection, the reproduction and development of reptiles is considered more progressive than that of amphibians?
The appearance of internal fertilization and egg shells in reptiles is the most important adaptation to the terrestrial way of life and, accordingly, a progressive sign. Most of their representatives reproduce by laying eggs covered with a leathery shell (in lizards and snakes) or calcareous shells (in crocodiles and turtles), but the so-called ovoviviparity is also observed, during which the hatchlings from the eggs (release them from the egg membranes) occur in mother's body. Oviparous production is characteristic of reptile species living in temperate climate zone(many lizards, the common viper, some snakes), or those that have gone completely aquatic (sea snakes).
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1. How do bony fish differ from cartilaginous ones?
2. Why are bone groups more numerous than cartilaginous ones?
3. What do all bony fish have in common?
Features of the external and internal structure, biology and ecology make it possible to single out some systematic groups among the diversity of fish. The most significant of them are the following.
Squad Sturgeon, or osteocartilaginous,- a small group of fish (Fig. 91). In the structure of sturgeons, ancient signs have been preserved, emphasizing their similarity with cartilaginous fish. Throughout life, sturgeons retain a notochord, an osseous-cartilaginous skeleton. The body is elongated, the head begins with a flattened snout, on the lower side of which there are two pairs of antennae and a mouth in the form of a transverse semilunar slit. The jaws are devoid of teeth. In the skin layer on the sides along the body and on the ridge there are five rows of large bone plaques, small bone plates are randomly scattered between them. Breast and ventral fins attached to the body horizontally. The caudal fin is unequal, reminiscent of a shark's tail. There is a swim bladder.
Family representatives sturgeons found mainly in the northern hemisphere of temperate latitudes of Europe, northern Asia and North America. As an adult, these fish spend most of their lives in the seas. Baikal sturgeon, American lake sturgeon and sterlet are considered freshwater fish. In spring or autumn, sturgeon for breeding come from the seas into the rivers: Volga, Don, Ural, Ob, Yenisei, Lena, etc. Individuals that entered the rivers in autumn overwinter in them and spawn the next year in the spring, simultaneously with the newly approached. Hatched larvae, growing sturgeon fry with the current of water are gradually carried to the mouth of the rivers, and then to the seas.
Rice. 91. Sturgeons
Sturgeons feed on mollusks, worms, crustaceans, larvae of aquatic insects, mainly mosquitoes. Far Eastern Kaluga and European Beluga are predators. They feed on small and large fish. At autopsy, a large number of herring, roach, chum salmon and even ducks were found in their stomachs.
Sturgeon meat is valued for its excellent taste. It is eaten fresh, salted, smoked. Sturgeon caviar is a very valuable nutritious product.
Rice. 92. Herring
Sturgeons are caught in Russia, Iran, the USA, France, Spain and a number of other countries. The Russians catch them mainly in the Caspian and Azov Seas, the rivers of Siberia and the Far East.
Sturgeons have always been poached. And the deterioration of the ecological state of many rivers, the construction of hydroelectric dams on them led to the extinction of fish. Hydroelectric power plants cause especially great damage to the sturgeon population, since only a few individuals through bypass channels and through fish elevators get above the dam.
Order Herring. The fish of this order have an elongated body, slightly compressed laterally (Fig. 92). The color of the back is dark blue or greenish, the belly is white with a silver tint. Paired and unpaired fins are soft. The lateral line is not visible. The body length is usually 5–75 cm, sometimes reaching 5 m.
Most of the herring species live in the seas, there are also anadromous ones - moving for reproduction from the seas to the rivers and vice versa. Few representatives of the detachment live in fresh water. They feed on planktonic invertebrates. Large individuals, as a rule, are predators that eat small fish.
Rice. 93. Salmon
The order consists of three families. The most famous fish from the family herring, relatively small or medium in size, usually 35–45 cm long, less often more. Herring live mainly in the seas. Commercial value have oceanic (Atlantic, Baltic, White Sea, Pacific) herring, sardine, willow. The smallest fish of commercial importance are sprat and tyulka, living in the Baltic, Black and Caspian Seas.
Order Salmonformes. This includes fish that look like herring-like fish, from 2.5 cm to 1.5 m long (Fig. 93). They live in the seas, feed, grow, reach sexual maturity, but enter rivers for reproduction. Chum salmon, pink salmon, sockeye salmon and others from the salmon family spawn in the rivers of the Far East; salmon, trout- in the rivers of the European North; chinook salmon- usually in the rivers of Alaska. All salmon are commercial fish, highly valued for their tasty meat and caviar. No less valuable are freshwater: trout, Baikal omul, Chud whitefish, vendace. Many of the salmon are bred in special fish farms.
Rice. 94. Cypriniformes
Order Cyprinidae. Representatives of the order (Fig. 94) are in many ways similar to the herring-like ones, but differ from them in some anatomical features. The number of species in the order is about 15% of all bony fish.
Among cyprinids there are herbivores, carnivores and omnivores. There are several types of predatory fish piranha, living in rivers South America. Dangerous for the life of animals and humans are common piranha, up to 30 cm long, and eastern brazilian big piranha, 60 cm long. All piranhas have sharp teeth that allow them to tear pieces of meat from the body of a victim that has fallen into the water.
Rice. 95. Perciformes
Predatory fish include electric eel. The body length of the fish is 1–1.5 m, sometimes more. The skin is bare, there are no scales. Eel lives in water bodies with a minimum oxygen content in the water. In the process of evolution, eels have developed the ability to absorb oxygen from the air: for this, the eel rises to the surface of the water several times within an hour and captures air with its mouth.
Electric eel has developed electrical organs. They are comparable to electric batteries located on the sides of the body from head to tail and giving an average voltage of 350 V at a current strength of 3 / 4 A. Electric organs serve as protection against enemies and for obtaining food. The electric field at the moment of discharge spreads in a diameter of 5–10 m from the eel. Animals that fall into the field of action of the discharge are paralyzed and become the prey of an electric eel.
In the water bodies of Russia, the most common representatives of cyprinids are roach, dace, asp, tench, barbel, bream, fish, bleak, sabrefish, carp, crucian carp, grass carp, all are of great commercial importance. A number of species are artificially bred in pond farms. In recent years, in most countries, including Russia, they began to breed such herbivorous fish as cupid, silver carp and their hybrids: labeo, barbels, catleys, cirrhines. Some tropical cyprinids with beautiful bright colors have become objects of keeping in aquariums. Over the years, breeders have bred colorful, varied goldfish from silver carp.
Order Perciformes - the most numerous in species composition a group of fish (Fig. 95). They are distributed in water bodies of all continents and in the oceans. A characteristic feature of perciformes is the presence of two dorsal fins with sharp spines. Some of them have no swim bladder. Body length from 1 cm to 5 m and weight from less than a gram to 1000 kg or more. For example, moon fish it can be up to 3 m long and weighing up to 1400 kg. The most common families are: rock perches; perch with childbirth zander, perch, ruff; scad; crucian carp; notothenic; catfish; goby; sailboats. Almost all fish of the perch-like order are edible and are objects of trade, as well as amateur fishing. Small fish of this group perfectly live and breed in aquariums.
From modern lungfish known: protopters from Africa, lepidosiren, or flake, from South America, neoceratodes, or cattail, from northeast Australia (Fig. 96). Regardless geographical location all lungfish live in shallow, slow-flowing rivers, swampy lowlands densely overgrown with vegetation.
Rice. 96. Lungfish
Rice. 97. Coelacanth coelacanth fish
Such reservoirs dry up during the year during the drought period and are filled with water for several months during the rains. Fish are considered ancient and are characterized by a primitive organization. They are well adapted to life in waters with a low oxygen content, and in the absence of water they can switch to pulmonary respiration.
About 400 million years ago, in the seas and fresh waters of our planet, lobe-finned fish(Fig. 97). They were represented by a large group of primitive bone fish. Until recently, it was believed that representatives of the Loop-finned fish became extinct about 7 million years ago. In 1938 southern shores Africa, in the Indian Ocean, the first instance of an unknown fish was caught from a depth of 70 m. Ichthyologist L. B. Smith, who first described a living "fossil" lobe-finned fish, called it coelacanth. The second specimen of the lobe-finned fish was caught with a line from a depth of 15 m in the same area. By 1980, more than 70 coelacanths had been caught.
Coelacanths reproduce by live birth. Like their distant ancestors, coelacanths have skeletal formations in paired limbs, equipped with powerful muscles. These fish have no practical commercial value.
Bony fish: Sturgeon, Herring, Salmon, Carp, Perch.
Questions
1. What biological features allowed fish to populate almost all the water bodies of the planet?
2. What species of sturgeons were distributed before or live now in the water bodies of your area?
3. What are the similarities between sharks and sturgeons?
4. What are the main differences between sturgeons and sharks?
5. What are the structural features of the living "fossil" coelacanth fish coelacanth?
6. What kind of fish is used in the fight against malaria? What is this type of struggle called?
7. What bony fish are protected in your area?
8. Why are aquarium fish attractive to keep?
Do you know that…
The largest of the sturgeons are the Far Eastern kaluga from the Amur basin and the European beluga living in the Caspian, Black, Azov and Adriatic Seas, up to 4 or more in length, and weighing up to 1000 kg. Commercial forms weighing 70–80 kg. Females spawn more than 9 thousand eggs. The life expectancy of these fish is over 100 years.
The smallest representative of sturgeons is pseudoshovelnose, living in the basins of the Amudarya and Syrdarya rivers, weighing less than 1 kg.
1. Why did the animals of this class get the names of amphibians, legless, tailed, tailless?
2. What types of amphibians are found in your area?
general characteristics. Class amphibians, or amphibian, includes animals adapted to life both on land and in water (Fig. 98). On land, most of them are found in adulthood, and the reproduction, growth and development of tadpole larvae takes place in the aquatic environment. Amphibians appeared about 350 million years ago, apparently from ancient lobe-finned fish. They were the first terrestrial vertebrates. They moved on land with the help of paired limbs, breathed with the help of lungs and skin.
The body of modern amphibians is divided into the head, trunk and limbs. The head has a pair of nostrils for breathing. atmospheric air, a pair of eyes protected by eyelids. The skin is naked (frogs, tree frogs), moist from the mucus secreted by special glands (a necessary condition for skin respiration), cool due to constant evaporation of moisture from its surface, keratinized (toads). They breathe air oxygen through the lungs, as well as oxygen dissolved in water through the skin. There are representatives with external gills (see Fig. 102). Blood flows through two circles of blood circulation. The heart of adult amphibians is three-chambered.
Rice. 98. Amphibians
The body temperature is unstable and depends on the ambient temperature, so all amphibians are active only in the warm season of the day and year. When the ambient temperature drops, they fall into a stupor. Animals are dioecious. Fertilization is internal or external. The eggs laid by the female develop in water. The larvae emerging from the eggs do not resemble adult amphibians (Fig. 99) and are similar to fish larvae. They breathe with external gills. The heart of the larvae, like that of fish, is two-chambered. One circle of blood circulation. There is a side line. Movement in water is carried out due to the bends of the tail flattened from the sides. After 2–3 months, the tadpole larva turns into an adult animal.
Amphibians destroy a large number of insects, including blood-sucking ones, and their larvae. They serve as food for many animals and even humans. The frog is an indispensable object of laboratory research. Many species are rare and protected.
Rice. 99. Amphibian larvae
Amphibians are the smallest class of vertebrates. About 4 thousand species are known. All species are grouped into three orders: Legless, Tailed and Tailless.
Squad Legless(Fig. 100) consists of one family worm. The homeland of legless amphibians is the tropical part of Africa, South America and South Asia, the islands of the Indian and Pacific Oceans. Except for the South American caecilians, who live permanently in the water, all other members of the family are underground inhabitants and are found in moist soil at a depth of 30–60 cm.
Rice. 100. Legless amphibians
Rice. 101. Tailed amphibians
These amphibians have a worm-like, cylindrical body, slightly flattened in the dorsal-ventral direction. The skin is naked, abundantly supplied with numerous mucous poisonous glands. From above, the body is divided into many transverse rings, in appearance resembling segments of earthworms. Worms do not have limbs and a tail, their head is small, imperceptibly passing into the body, there are no organs of vision and hearing. Looking for food, worms, like earthworms, make passages in the ground. They feed on invertebrates: worms, snails, larvae and adult insects. They can even attack small snakes. Food is found with the help of well-developed organs of smell and touch.
Squad Tailed(Fig. 101) unites amphibians living north of the equator, in the temperate zone of the Eastern and Western hemispheres. South of the equator, in South America, there is only a small group salamander. The elongated spindle-shaped body of tailed amphibians imperceptibly passes into a long tail, rounded in salamanders and ambist, laterally compressed newts, proteas, axolotls. Curving the tail to the right and left helps these amphibians move in the water. On land, representatives of the caudate move with the help of two pairs of underdeveloped limbs. The fingers at the ends of the limbs of many species are equipped with an easily extensible leathery membrane and are devoid of claws. North American sirens do not have hind limbs.
Rice. 102. Representative of tailed amphibians - striped siren
Breathing in adult tailed amphibians is provided by the lungs, skin and mucous membrane of the oral cavity. Representatives of the detachment constantly living in water breathe with the help of both lungs and external gills. The gills look like feathery branches located on the sides of the head (Fig. 102).
Fertilization is internal and external. Females lay from 2–5 to 600–700 eggs (eggs) in water or in damp places. Egg development lasts 2-3 months. The emerging larvae are similar in appearance and mode of movement to fish larvae.
Detachment Tailless- the most numerous group of amphibians, numbering about 3 thousand species. They are distributed throughout the globe, found on all continents and islands of both hemispheres, with the exception of Antarctica and the northernmost islands. Of the order of tailless amphibians, the most famous are frogs, toads, tree frogs, toads, spadefoot(Fig. 103). Unlike representatives of other orders, the tailless have mastered the land to a greater extent, but have not lost contact with water. These amphibians have a number of specific adaptations to living conditions.
The body is short, squat. The head is wide, without a neck, merged with the body. There is no tail. The skin is naked, equipped with many glands, the secret of which abundantly moisturizes the surface of the body. The head has a pair of movable eyes with nictitating membranes and a pair of nostrils at the tip of the muzzle. They breathe atmospheric air with the help of the lungs and through the skin. The translational movement in the water is intermittent due to the work of long limbs equipped with swimming membranes, turned into flippers. The forelimbs are shorter than the hind limbs, when swimming they are pressed against the body. On the ground, tailless amphibians prefer to move by jumping, using powerful hind limbs. These animals are active throughout the day. Adults lead a predatory lifestyle.
Rice. 103. Tailless amphibians
Tailless amphibians feed on spiders, ants, crustaceans, earthworms, terrestrial and aquatic mollusks and insects. Food is actively searched for with the help of vision in water and on land. They catch flying insects. Small teeth and a sticky tongue, which is attached at the base of the mouth with its front end and is doubled in the oral cavity, help amphibians to grasp and hold prey. At the moment of approaching prey, it is thrown far ahead (Fig. 104).
Tailless amphibians breed in water. The females lay eggs, while the males produce milk. Fertilization of eggs is external. The tadpoles emerging from the eggs are similar to fish and feed on unicellular blue-green algae and protozoa during the first days of life. After 50–60 days in warm water and 80–85 days in cold water, the tadpole turns into a small frog that is able to leave the reservoir and go to land.
Of the real frogs, the most common lake and pond, whose life is mostly associated with water. herbal and moored frogs, on the contrary, use water mainly during the breeding season. In summer, in search of food, they leave the reservoir and live on land.
Amphibians: Legless, Tailed, Tailless. Tadpole.
Rice. 104. Tongue of a frog at the moment of catching an insect
Questions
1. What are the similarities and differences between amphibians and fish?
2. What is the importance of amphibians in nature?
3. What features allow amphibians to live both on land and in water?
4. What is the difference between development and transformation in amphibians and insects?
Tasks
Using various sources information, list the amphibians that are protected in your area.
Do you know that…
Toads are associated with water only during the breeding season. The surface of the skin of toads is keratinized, so the evaporation of moisture through the skin does not occur. Breathing is carried out to a greater extent with the help of the lungs, which allows the toads to go far from the reservoir. In our latitudes, common and green toads are predominantly common.
1. Why are these animals called reptiles?
2. Which of them live in your area?
General characteristics. Most representatives of the class of reptiles are terrestrial animals. The skin is dry, externally covered with horny scales, scutes. Skin glands are usually absent. Reptiles breathe with the help of lungs that have a cellular structure. The heart is three-chambered, consists of a ventricle and two atria. Crocodiles have four chambers. Two circles of blood circulation. The brain has a more complex structure than that of amphibians. The excretory organs are the kidneys. The body temperature is unstable, and therefore the activity of these animals depends on the ambient temperature. Reptiles have separate sexes. Fertilization is internal. Most representatives of this class reproduce by laying fertilized eggs covered with a leathery shell (for lizards and snakes) or calcareous shells (for crocodiles and turtles), but there are also viviparous.
Most reptiles are carnivores or insectivores, while terrestrial turtles feed primarily on plants. Modern reptiles descended from ancient reptiles - cotylosaurs, who lived about 285 million years ago, which still retained in their structure the features characteristic of the oldest tailed amphibians - stegocephalians. The time from 70 to 255 million years ago is considered the era of prosperity and diversity of reptiles. Lived on dry land dinosaurs, floating dominated the water ichthyosaurs, in the air - flying pterosaurs(Fig. 105).
About 100 million years ago, a global drop in temperature occurred on our planet and a prolonged cooling set in. This dramatically changed the environmental conditions and led to mass death reptiles. There are about 7 thousand species of modern reptiles, united in 4 orders: Scaly, Turtles, Crocodiles, Beakheads.
Order Scaly (Fig. 106) - the most diverse and numerous in terms of the number of species. It includes lizards, agamas, geckos, monitor lizards, chameleons and snakes. Animals of this order are widely distributed on the continents and islands. Found in all parts of the world.
Rice. 105. Extinct ancient reptiles
Lizards. The body of lizards is elongated, slightly compressed laterally. It consists of a head, a body, two pairs of movable, tenacious limbs with claws and a long tail. Yellowbelly and spindle have no limbs and external structure look like snakes. The skin of lizards is covered on top with keratinized scales, spikes, shields or ridges that protect them from mechanical damage and moisture loss. The head is movably connected to the body. The eyes are equipped with movable eyelids and a nictitating membrane.
Rice. 106. Scaled reptiles
Lizards distinguish objects well at a distance of several tens of centimeters, but at the time of hunting they react only to moving prey. They hear well. Small teeth are located on firmly connected jaws. The forked tip of the tongue performs the functions of smell, touch, and taste.
Of the lizards that have limbs, the most common quick, viviparous, green, from the legless - the yellow-bellied and the spindle.
In the spring, after the winter awakening, the lizards breed, laying from 6 to 16 eggs in specially prepared small depressions, well lit by the sun. After 50–60 days, small lizards hatch from the eggs. They feed on a variety of insects and their larvae, earthworms, and land mollusks. The viviparous lizard, in contrast to the lizard, prefers damp areas of swamps (more often peat bogs), wet areas of forests. She is not picky about temperature, which allows her to live in the northern regions, almost at the Arctic Circle. Mating takes place in early spring in April-May. In the body of a female, embryos develop within 90 days and are born 8–9 individuals alive.
monitor lizards- a family of large lizards. They live in Africa, South Asia, Australia, on the islands of Oceania. Active during the day. Although they seem slow, they are able to run fast on muscular legs at a speed of 100-120 m / min. A long movable tail is often used when catching prey: the monitor lizard knocks the victim down with it. The tongue is long, partially forked. Monitor lizards are predators: they feed mainly on invertebrates, but they can catch lizards, snakes, birds, rodents, eat eggs of birds and turtles. In the desert sands Central Asia and southern Kazakhstan lives gray monitor lizard up to 1.5 m long.
snakes- scaly reptiles, with a long cylindrical body, an ovoid or triangular head and tail (Fig. 107). The limbs are missing. Only boas and pythons the remains of the hind limbs are preserved in the form of two slightly protruding bones from under the scales. The skin is covered with horny scales, different in size, shape and location. Body length ranges from 12 cm (at burrowing snakes) up to 10 m (for boas).
Snakes move pretty fast. They have developed a special mechanism of movement by means of lateral bends of the spine and ribs, which, with their lower ends, are able to move forward and backward. The ventral transverse shields are also used, clinging to the unevenness of the soil.
Rice. 107. Snakes
The organs of vision are the eyes, which are hidden under a transparent leathery film formed by fused eyelids. The pupil of the eye is in the form of a vertical slit. Snakes have poor vision and poor hearing. They have no external auditory opening.
In the oral cavity is a thin and long tongue, forked at the end. Like lizards, it is an organ of touch, smell, and taste. The tongue is mobile, through a semicircular opening in the upper jaw it is able to protrude outward with the mouth closed. By sticking out and removing the tongue, the snake receives information about the smells in the air, and if it touches the surrounding objects with its tongue, then about their surface, shape and taste. On the lower and upper jaws there are relatively thin teeth of the same type. They serve to capture prey and hold it. From non-venomous snakes water snakes and yellow-bellied snakes have small sharp teeth capable of pushing live prey into the esophagus. Boas, before swallowing, strangle the victim, wrapping it in rings of a muscular body. Poisonous snakes in the upper jaw have two particularly prominent poisonous teeth. Venom is produced by paired venom glands located on both sides of the head behind the eyes. Their ducts are connected with poisonous teeth.
All snakes are predators. They are able to swallow prey many times the thickness of their body. This is facilitated by movable jaws. The lower jaw is movably connected to the bones of the skull, moves forward and goes back, as if on a hinge. Its halves are connected on the chin by a flexible ligament and are able to move apart to the sides.
Approximately 1-2 times a year, snakes molt. The molt proceeds for half an hour or a little more and ends with the shedding of the upper cover - creep out. The molting process itself begins a few days before shedding the skin. It is accompanied by clouding of the eyes, loss of skin luster, sedentary state. The worn cover of the snake usually sheds gradually. At this moment, she vigorously rubs against the branches of shrubs and trees or against stones. The skin is shifted from the head and body in a “stocking” due to the snake crawling and rubbing against protruding solid objects. Everything ends with the complete liberation of the body from the old skin.
Snakes of most species have a protective coloration that is in harmony with the color of the environment. This is necessary for disguise at the time of hunting. Yellowish-sandy coloration is characteristic of many desert species. Coloring tiger python and Gaboon viper bright, colorful, like leaf litter rainforest, which makes the snakes in it invisible. Some snakes have a bright, very contrasting pattern. His snakes demonstrate for intimidation at the moment of danger. For example, spectacle snake from the genus cobras(Fig. 108).
Rice. 108. Spectacle snake
Snakes are common in all parts of the world, but in areas with a hot climate they are much more numerous. They live in various ecological conditions - forests, steppes, deserts, in the foothills and mountains.
Snakes mainly lead a terrestrial existence, but some species live underground, in water, on trees. When adverse conditions occur, for example, as a result of a cold snap, snakes hibernate. They reproduce by laying eggs. Some species are ovoviviparous.
The economic importance of snakes is largely underestimated. Many species of snakes feed on rodents, regulating their numbers in nature. Various medicines are made from snake venom.
Questions
1. What acquired structural features allowed reptiles to completely switch to a terrestrial way of life?
2. What are the characteristic features of snakes?
3. What functions does the tongue of snakes fork at the end perform?
4. What animals belong to the order Scaly? What is their significance in nature and human life?
5. In this connection, the reproduction and development of reptiles is considered more progressive than that of amphibians?
Tasks
1. Based on the knowledge gained in the OBZh course, name the first aid measures for snake bites.
2. Find out which reptiles are protected in your area.
3. Think and discuss with your classmates why the medical emblem has a snake.
Do you know that…
The giant monitor lizard from the Komodo and Flores islands has a body length of up to 3 m. This animal hunts birds, small animals, and eats their corpses. Along with large monitor lizards, small monitor lizards are also known, for example, the length of the Australian short-tailed monitor does not exceed 20 cm.
Poisonous snakes are caught and kept to obtain poison in special nurseries. They are found in tropical Asia, southern Africa, South America, and Central Asia. They contain mainly cobras, gyurz, steppe vipers, etc.
Snakes are one of the most peculiar creatures on earth. Their unusual appearance, an original way of movement, many remarkable features of behavior, and finally, the toxicity of many species - all this has long attracted attention and aroused keen interest among people. Among the various peoples the globe There are many legends, fairy tales and myths about snakes. All these fantasies, reinforced at times by an unconscious superstitious fear of snakes, are so closely intertwined with real facts that many "true" stories about snakes are much more fantastic than any myths. The study of snakes gradually exposes the legends and at the same time reveals new remarkable features in the structure and lifestyle of these animals.
At first glance, it seems that snakes are easy to distinguish in appearance from all other reptiles. Indeed, they have a long, legless torso, dressed in scales, their eyes are always covered with a transparent leathery shell, they lack an external ear. However, all these structural features can also be found in various lizards. Lizards and snakes are closely related animals, so they are classified only in different suborders within the general squamous order (Squamata). 
About thirty signs of external and internal structure distinguish snakes from lizards, but almost all of them "as an exception" are also found in the latter. Thus, only by the complex of all these differences can one reliably separate two suborders of scaly reptiles.
The skull of snakes has the most characteristic and stable features of these animals, which distinguish them from lizards. The structure of the skull provides exceptional extensibility of the mouth of snakes, which allows them to swallow whole prey, which is much thicker than their body.
The bones of the facial part of the skull of most species of snakes are movably connected to each other, and the lower jaw is suspended from the skull by highly extensible ligaments. The elastic ligament also connects the right and left halves of the lower jaw. In addition, the snake's brain is entirely enclosed in a bone capsule, and the interorbital septum is not developed.
The teeth of snakes are well developed and serve to bite, capture prey and push it into the esophagus, but by no means for chewing or tearing the prey, since the prey is swallowed whole. Therefore, all teeth are relatively thin, sharp and bent back. They are located on the upper and lower jaws, and in many snakes also on the palatine, pterygoid and premaxillary bones. In addition to the usual solid teeth, snakes of some families have furrowed or tubular teeth that serve to introduce poison into the body of the victim. Furrowed teeth located in the back of the upper jaw are characteristic of poisonous snakes. Aspid and sea snakes have short fixed tubular teeth in front of the mouth, while vipers and pit vipers have long and mobile tubular teeth mounted on a very short maxillary bone that can rotate. At the same time, the venom-conducting fangs, with the mouth closed, lie along the jaw, pointing back, but when the mouth opens, they become perpendicular, taking a "combat" position.
The belt of the forelimbs in snakes is completely absent, and from the belt of the hind limbs in some snakes (boas, valkovy snakes, blind snakes, narrow-mouthed snakes), small bone rudiments of the pelvis are preserved. In boas and roller snakes, the rudiments of the hind limbs themselves have also been preserved in the form of paired claws on the sides of the anus.
The spine of snakes, due to the disappearance of the limb belts, is not clearly divided into sections. The number of vertebrae is very large, from 141 in the thickest and shortest snakes to 435 in the longest and thinnest. The ribs have exceptional mobility. The sternum is absent, and therefore the ribs can diverge widely to the sides, passing large prey through the digestive tract. In addition, many snakes are able to spread their ribs to the sides, flattening the body, when defending.
The internal organs have undergone a significant change in accordance with the elongated shape of the legless body. All of them have an elongated shape and are arranged asymmetrically. In addition, some of the paired organs lost one half and became unpaired. For example, in the most primitive snakes, both lungs are developed, but the right one is always larger than the left; in most snakes, the left lung completely disappears. Vipers and some other snakes, in addition to the right lung, also have the so-called "tracheal lung", formed by the expanded back part of the trachea. The lung itself in its back part is transformed into a thin-walled air reservoir. It is very stretchy, and the snake can swell strongly when inhaling, and when exhaling, it can emit a loud and prolonged hiss.
The esophagus of snakes is very muscular, which makes it easier to push food into the stomach, which is an elongated bag that passes into a relatively short intestine. The kidneys are strongly elongated in length, and the bladder is absent. The testicles are also elongated; the copulatory organ of males is paired sacs, usually equipped with spines of various sizes and shapes. These sacs lie under the skin behind the anus and turn outwards when aroused.
The nervous system of snakes is characterized by a small brain and a powerful, long spinal cord. This causes, on the one hand, the primitiveness of higher nervous activity and, on the other hand, high coordination, accuracy and reactivity of body muscle movements.
The most important sense organ of snakes is the tongue in combination with Jacobson's organ. The paired Jacobson's organ is a thin chemical analyzer and has two outlets on the upper palate. The snake's tongue protrudes through the semicircular notch of the upper jaw, flutters in the air for several seconds, lightly touching nearby objects with forked tips, and then is drawn inward. Here, the ends of the tongue are thrust into the holes of the Jacobson's organ, and the snake receives information about negligible amounts ("traces") of substances in the air and on the substrate. Thus, by alternately sticking out and retracting its tongue, the snake moves quickly and confidently along the trail of prey, looking for prey, a partner, or a source of water.
Unfortunately, still many people believe; the snake's tongue is a "deadly sting" and, seeing its protruding tips, they confidently declare the snake poisonous and, at every opportunity, sometimes kill a completely harmless animal.
The eyes also play a large role in the orientation of snakes, but most of the vision is not sharp. This, in particular, is due to the fact that the eye is covered with a thin and transparent leathery film formed from the fused eyelids. This film comes off the eye along with the rest of the cuticle during molting. Therefore, before molting, the eyes of snakes become cloudy (the surface layer of the film peels off), and after molting they become especially transparent. The dry film covering the eye gives the snake's gaze the seeming stillness and coldness that frightens so many people and creates myths about the hypnotic power of the snake's gaze. The pupil of the eye in diurnal snakes is round, while in twilight and nocturnal snakes it is often extended into a vertical slit. It has a special shape in whip-shaped snakes, most of all resembling a horizontally located keyhole. This structure of the pupil provides the ability for binocular vision, in which up to 45 ° field of view covers both eyes at once.
The sense of smell of snakes is well developed and serves as one of their guiding senses. The nostrils are located on the lateral or upper edge of the muzzle. In marine, as well as in some sand snakes, the nostrils can be closed with special valves, which prevents water from entering when diving or sand when crawling in its thickness.
The hearing organs are greatly weakened: there is no external auditory opening at all, and the middle ear is also simplified. Only the inner ear is fully developed. Therefore, snakes hear very poorly the sounds propagating through the air, and in the ordinary sense of the word they are almost deaf.
Some snakes have thermal sense organs, or remote thermoreceptors, which allow them to detect heat from the body of prey at a distance. In pythons, they are represented by shallow pits on the upper labials; in African vipers of the genus Bitis, they have the form of cup-shaped depressions immediately behind the nostrils. These organs are especially highly developed in pit vipers. The paired thermolocator is visible from the outside in the form of pits on the sides of the muzzle between the nostrils and the eye.
The snake's body is covered with horny shields and scales. On the head of many snakes, large shields of a regular and constant shape are grouped in a strict; order typical for each species, and serve as an important feature for the scientific description and definition of species.
The body from above and from the sides is covered with rounded diamond-shaped scales, which are located in longitudinal and diagonal rows, and usually the anterior scales slightly overlap the posterior ones. In some species, the scales may have a hexagonal or trihedral shape and be located in the same plane, without overlap (some sea and warty snakes). Horny scales are smooth or have a more or less pronounced longitudinal keel. Between the horny scales of neighboring longitudinal rows there are areas of thin and soft skin, collected in a small fold hidden under the scales. When swallowing large prey, the longitudinal rows of horny scales diverge, the leathery folds straighten out and the body greatly increases in diameter. The scales of one longitudinal row, on the contrary, are firmly connected to each other.
The belly of the snakes is covered with large transversely elongated shields. Only in some aquatic and burrowing species (warty, part of marine, blind snakes, narrow-mouthed) the body from below, as well as from above, is dressed with small scales. The abdominal shields are interconnected by soft folds of skin, and when large food is swallowed, these folds straighten out, and the abdominal shields diverge in the longitudinal direction. Thus, the covers of the snake have a large extensibility, and on the back and sides - transverse, and on the belly - longitudinal.
The top layer of the skin periodically exfoliates, and molting occurs. When molting, the exfoliated epidermis departs first at the front end of the muzzle, and then is removed from the body of the snake with a stocking. A molting snake is actively moving, rubbing its head against the soil and stones, crawling through cracks, pulling off its old skin. Before molting, the color of the snake becomes whitish, and the eyes become cloudy, but after molting, the snake sparkles with bright fresh colors. Healthy snakes molt 2-4 times a year, and the crawl comes out entirely, while in sick and emaciated snakes, molting occurs more often and the old skin peels off in pieces.
In rattlesnakes, when molting, the end scales remain on the tail in the form of caps and form a special ratchet, which they use to warn large enemies.
The coloration of snakes is very diverse and for the most part adaptable to the color of the natural environment. Such is the green color of many tree snakes, yellowish-sandy - in desert species. The coloration of some species, such as the tiger python or the Gaboon viper, seems bright and conspicuous to us when we see them in the zoo. But in natural conditions, among the motley leaf litter under the canopy of the rainforest, this coloring perfectly hides the snake, dismembering and making invisible the true contours of its body.
Some species, however, have bright colors that make them stand out even in their natural setting. These are primarily coral and garter snakes, royal snakes, in the color of which black, yellow and red transverse rings alternate. This coloring is a warning. The extreme resemblance of non-venomous royal snakes and poisonous asps is often cited as an example of imitative resemblance - mimicry. However, such an explanation does not stand up to criticism: firstly, coral asps very rarely and reluctantly bite and lead a twilight lifestyle, so predators cannot develop a clear idea about the danger of this color; secondly, the alleged "imitators" - king snakes - are much more widespread than their imaginary "model".
Many snakes that are colored patronizingly have areas of the body with a bright pattern, which they show only at the moment of danger. Such is the spectacled snake - a cobra straightening cervical region with a clear pattern of "glasses" on the dorsal side. In other species of snakes, the underside of the tail is painted bright orange, and when defending, the snake raises its tail with the bright side to the enemy and shakes it, sometimes even makes "lunges" with its tail, as if wanting to bite.
Usually, young snakes are colored more brightly and contrastingly, while adults are more uniformly colored.
According to WWW.ANIMALS.Ru
Snakes are animals with a long, narrow and flexible body. They do not have legs, paws, arms, wings or fins. There is only a head, body and tail. But does a snake have a skeleton? Let's find out how the body of these reptiles is arranged.
snake features
Snakes belong to the class of reptiles. They live all over the earth, except for Antarctica, New Zealand, Ireland and some Pacific islands. They are also not found beyond the Arctic Circle and prefer the warm tropics. These animals can live in water, desert, rocky mountains and dense forests.
The body of the snake is elongated and, depending on the species, has a length of several centimeters to 7-8 meters. Their skin is covered with scales, the shape and location of which is not the same and is a specific feature.
They do not have movable eyelids, outer and middle ear. They hear poorly, but they distinguish vibrations perfectly. Their body is very sensitive to vibrations, and since it is often in direct contact with the ground, the animals feel even slight shaking of the earth's crust.
Vision is not well developed in all snakes. They need it mainly in order to distinguish between movement. Worst of all, representatives of species living underground see. Special receptors for thermal vision help snakes recognize prey. They are located in their facial part under the eyes (in pythons, vipers) or under the nostrils.
Does a snake have a skeleton?
Snakes are predators. Their food is very diverse: small rodents, birds, eggs, insects, amphibians, fish, crustaceans. Large snakes can even bite a leopard or a wild boar. They usually swallow their prey whole, pulling on it like a stocking. From the outside it may seem that they have absolutely no bones, and the body consists of only muscles.
To understand whether snakes have a skeleton, it is enough to refer to their classification. In biology, they have long been identified, which means that at least this part of the skeleton is present in them. Together with turtles, crocodiles, they belong to, occupying an intermediate link between amphibians and birds.
The structure of the skeleton of a snake has some similarities, but differs in many ways from other members of the class. Unlike amphibians, reptiles have five sections of the spine (cervical, trunk, lumbar, sacral, and caudal).
The cervical region consists of 7-10 movably connected vertebrae, allowing not only to raise and lower, but also to turn the head. The body usually has 16-25 vertebrae, each of which is attached to a pair of ribs. The tail vertebrae (up to 40) decrease in size towards the tip of the tail.
The skull of reptiles is more ossified and hard than that of amphibians. Its axial and visceral sections are fused in adults. Most representatives have a sternum, pelvis and two limb belts.
Signed snake skeleton
The main distinguishing feature of snakes is the absence of front and rear limbs. They move by crawling on the ground, fully relying on the entire body. Limb rudiments in the form of small processes are present in the structure of some species, for example, pythons and boas.
In other snakes, the skeleton consists of a skull, torso, tail and ribs. The body section is greatly elongated and contains much more "details" than other reptiles. So, they have from 140 to 450 vertebrae. They are connected to each other by ligaments and form a very flexible structure that allows the animal to bend in all directions.
The sternum is completely absent in the skeleton of the snake. From each vertebra, ribs extend from both sides, which are not connected to each other. This allows you to increase the volume of the body several times when swallowing large foods.
The vertebrae and ribs are connected by elastic muscles, with the help of which the snake can even lift the body vertically. In the lower part of the trunk region, the ribs are gradually shortened, and in the caudal region they are absent altogether.
Scull
In all snakes, the bones of the brain box are movably connected. The articular, surangular and angular bones of the lower jaw are fused with each other, connected to the dentary by a movable joint. The lower jaw is attached to the upper ligament, which can be greatly stretched to swallow large animals.
For the same purpose, the lower jaw itself consists of two bones, which are connected to each other only by a ligament, but not by a bone. In the process of eating prey, the snake alternately moves the left and right parts, pushing the food inside.
The skull of snakes has a unique structure. If the appearance of the spine and ribs is typical for the entire suborder, then the skull reveals the features of a particular species. For example, at rattlesnake the skeleton of the head has a triangular shape. In pythons, the head is elongated in the shape of an oval and slightly flattened, and the bones are much wider than those of the rattlesnake.
Teeth
Teeth are also a distinctive feature of a species or genus. Their shape and number depend on the lifestyle of the animal. Snakes need them not to chew, but to bite, capture and hold prey.
Animals swallow food, while not always waiting for her death. To prevent the victim from escaping, the teeth in the snake's mouth are angled and directed inward. This mechanism resembles a hook for catching fish and allows you to firmly dig into the prey.
The teeth of the snake are thin, sharp and are divided into three types: constrictor, or solid, grooved, or grooved, hollow, or tubular. The former are present, as a rule, in non-poisonous species. They are short and numerous. On the upper jaw they are arranged in two rows, and on the lower jaw - in one.
Furrowed teeth are located at the end of the upper jaw. They are longer than solid ones and are equipped with a hole through which poison enters. They are very similar to tubular teeth. They are also needed for injecting poison. They are fixed (with a permanent position) or erectile (pull out of the jaw groove when threatened).
snake venom
A large number of snakes are poisonous. They need such a dangerous tool not so much for protection as for immobilizing the victim. Usually two long poisonous teeth stand out clearly in the mouth, but in some species they are hidden in the depths of the mouth.
Poison is produced by special glands located at the temple. Through the channels, they are connected to hollow or embossed teeth and are activated at the right time. Separate representatives of rattlesnakes and vipers can remove their "stings".
Taipan snakes are the most dangerous to humans. They are common in Australia and New Guinea. Before a vaccine was found, mortality from their poison was noted in 90% of cases.
